The field of view is exactly the same between the games. BFV shows you the horizontal 4:3 FOV to the right, not the FOV based on your resolition.
You should in most cases keep the same USA setting. Say you go from a 4:3 monitor with USA 133 which means same movement to the edge of the monitor. You replace it with a 16:9 and keep the USA. You will now still have the same movement to point on the new monitor where the edge of the 4:3 monitor would have been, so in essence you keep the same sensitivity, but see a bit more on the sides.